Quaternary ammonium compounds and linear polymeric quaternary ammonium compounds are used to eliminate or inhibit the growth of bacteria and algae in fresh water supplies used in commercial and industrial operations, in cooling water used for many types of systems, and in swimming pools. The polymeric products are generally prepared by the reaction of dihalo compounds with ditertiary amines, and the molecular weights of the polymers are usually low and in the area of less than 10,000. The products of the reaction of dimethylamine with epichlorohydrin are also low molecular weight polymers that are effective against bacteria and algae in aqueous systems. Higher molecular weight polymers have generally been used as flocculants. It is generally recognized that the lower molecular weight polymers will have a higher toxicity to humans, animals and fish than the higher molecular weight products.
Panzer and Dixon obtained U.S. Pat. No. 3,738,945 and Reissue U.S. Pat. No. 28,807, which disclose a water dispersible polyquaternary polymer of essentially linear structure made from dimethylamine and epichlorohydrin. Later patents disclose processes for clarifying raw water using the polymers described by Panzer and Dixon. See U.S. Pat. No. 3,894,944. U.S. Pat. No. 3,894,947 covers the use of dimethylamine-epichlorohydrin polymers for flocculating industrial wastes. U.S. Pat. No. 3,975,347 relates to a process for the preparation of a 60 to 85% aqueous solution of a linear dimethylamine-epichlorohydrin polymer. U.S. Pat. No. 4,111,679 discloses a method for controlling microorganisms in industrial cooling water systems which comprises adding to the system a microbicidal amount of a polyquaternary amine of the formula ##STR1## where R.sub.1 and R.sub.2 are methyl or ethyl, X is Cl, Br, or I and n is from 3 to 10,000. The patentee states that the polyamines are made by reacting dimethylamine with epichlorohydrin as described in U.S. Pat. No. 3,738,945.
Another patent, U.S. Pat. No. 4,140,798, discloses a method of inhibiting microorganisms using a compound formed by the condensation of dimethylamine and epichlorohydrin in about a 1:1 molar ratio. Uses listed in the specification are recirculating water systems, such as paper mills, air conditioners, humidifiers, grinding lubricants, swimming pools and other uses.
All of the patents referring to the use of dimethylamine-epichlorohydrin polymers as microbicides refer to linear polymers. Even though the original Panzer and Dixon patent (U.S. Pat. No. 3,738,945) discloses cross-linked polymers, no mention is made of these polymers as possessing antimicrobial properties. When the original patent, U.S. Pat. No. 3,738,945, was reissued the linear polymers were included in Reissue U.S. Pat. No. 28,807, but the cross-linked polymers were included in Reissue U.S. Pat. No. 28,808. This latter Reissue lists the coreactants with dimethylamine and epichlorohydrin as ammonia, primary amines, alkylenediamines, such as ethylenediamine; polyethylenepolyamines, such as diethylenetriamine, triethylenetetramine, etc.; polyglycolamines, piperazines, heteroaromatic diamines, and aromatic diamines. The amount of the polyfunctional amines listed above is up to about 15 mole percent of the total moles of the dimethylamine, and the total of all amines is at least equimolar to the epichlorohydrin. U.S. Pat. No. 3,894,945 discloses a process for clarifying raw water with the polymers of Reissue U.S. Pat. No. 28,808, and U.S. Pat. No. 3,894,946 relates a process for flocculating industrial wastes with the same polymers.
Additional uses for the cross-linked polymers have been patented since 1975. These are included in U.S. Pat. Nos. 3,930,877, 4,104,161, 4,164,521, 4,147,627, 4,166,041, 4,606,773 and 4,769,155. Usually the lower molecular weight linear ionene polymers have been used as microbicides.